The present invention relates to a system for and method of determining the presence and operability of a relay and its associated components. More particularly, the invention includes a circuit and method for remotely checking the integrity not only of both windings of a dual coil latching relay, but also verifying the relay state (including whether the relay is on, off, or missing).
In various control systems, relays are placed at a considerable physical distance from the controller which ordinarily regulates energization and de-energization of those relays. Examples of such systems are described and illustrated in U.S. Pat. No. 4,394,655, issued Jul. 19, 1983; U.S. Pat. No. 4,470,047, issued Sep. 4, 1984; and U.S. Pat. No. 4,507,652, issued Mar. 26, 1985. All of these patents are titled "Bidirectional, Interactive Fire Detection System" and all are assigned to the assignee of this application. It will become apparent that the present invention finds particular utility with the systems taught in these patents, and also much wider application where remotely located relays must be supervised from a control point.
In the systems described in the references cited above, a controller issues commands over a pair of conductors to one or more transponders coupled to that same conductor pair. In turn the transponders both reply to the controller and, when commanded, take other action such as regulating a relay, a fan or blower, an alarm bell, a fire door, and so forth. Manifestly many of these functions have enormous importance to life safety and property conservation, and therefore it is highly desirable to know that the components connected to perform these important tasks will actually do so when called upon to operate.
It is therefore a principal consideration of the present invention to check the presence and operability of remotely positioned relays, and of the electrical circuitry associated with such relays.
The present invention is particularly useful for remotely supervising a dual coil latching relay which has first and second windings coupled to a pair of electrical conductors. The relay also includes at least one contact set for displacement as either relay winding is energized. A transponder, coupled both to the conductor pair and to the relay, provides a first supervisory pulse signal to the first relay winding in a first predetermined time period. The supervisory pulse signal is at a power level below that required to displace the relay contact set. A controller, also coupled to the conductor pair, includes sensing means operable during the first predetermined time period to sense the presence or absence of current flow through the first relay winding. The presence of current flow confirms both the presence and operability of the relay and of its associated circuitry.
The invention can also be practiced as a method for supervising a dual coil latching relay having a pair of windings coupled to a pair of electrical conductors at a location remote from a control point. The relay has at least one contact set for displacement as either relay winding is energized. In this method a supervisory pulse signal is provided to the first winding in a predetermined time period. The pulse signal is at a power level below that required to displace the relay contact set. Then, during the first predetermined time period, the presence and absence of current flow through the first relay winding is sensed, to confirm both the presence and operability of the relay and of its associated circuitry by noting the presence of current flow. Similar pulsing is done for the second relay winding, in a second predetermined time period time period, at a power level below that required to actuate the relay contact set.
According to another aspect of the invention, a method is provided to conserve energy by terminating energization of the just-energized relay winding as soon as the displaced contact set has completed its desired travel from one position to the other.